Modern engines employ various gas flow control for improved performance and operation of an internal combustion engine. For example, exhaust gas recirculation or EGR in an internal combustion engine is used to remove a portion of the exhaust gas stream downstream of the cylinders and introduce the portion of exhaust gas upstream of the cylinders. Conversely, post- or secondary air injection in an internal combustion engine is used to remove a portion of the combustion air, which may be fresh air or an air-fuel mixture, upstream of the cylinders and introduce the portion of combustion air downstream of the cylinders.